Fix ReadMagicAndReset.
ReadMagicAndReset is a function that is supposed to read a uint32_t
from the beginning of a file. However, it cannot handle the case where
the file offset of the fd is non-zero. Specifically, when an fd is
passed from dex2oat, dex2oat has probably read that file, causing the
file offset to be non-zero. This CL fixes the problem by resetting the
file offest before reading from the fd. Ideally, we should use `pread`,
but `ReadMagicAndReset` is part of `libartbase`, which has to support
Windows build where `pread` is not supported.
This change fixes odrefresh, which invokes dex2oat with fds.
Bug: 213446666
Test: atest odsign_e2e_tests
(cherry picked from commit 0628e784532303b27e062ed957494bfd7e858bd9)
Merged-In: Ib5dd8e2855a4f0a391afa5313cf3a2d12f1a3121
Change-Id: I6cfba0cfbcee0a1f914cbc661d2af428292a3533
diff --git a/libartbase/base/file_magic.cc b/libartbase/base/file_magic.cc
index 1471c59..21b762f 100644
--- a/libartbase/base/file_magic.cc
+++ b/libartbase/base/file_magic.cc
@@ -44,6 +44,10 @@
}
bool ReadMagicAndReset(int fd, uint32_t* magic, std::string* error_msg) {
+ if (lseek(fd, 0, SEEK_SET) != 0) {
+ *error_msg = StringPrintf("Failed to seek to beginning of file : %s", strerror(errno));
+ return false;
+ }
int n = TEMP_FAILURE_RETRY(read(fd, magic, sizeof(*magic)));
if (n != sizeof(*magic)) {
*error_msg = StringPrintf("Failed to find magic");
